What must we keep in mind with Utility bed swaps?

It is the GVW rating that determinate if you have to pull to the scales and RV are exempt this way or the other.
I went opposite way.
Bought my pickup with 10' utility bed and not only the bed floor was raised about 4 " above the frame, but I had to add another 4" planks under the camper to clear sides above the boxes.
That brought my total height above 13' and I was not comfortable with it.